"The way [season four] ends could function as a series finale, but there's one storyline left open that could end up as a cliffhanger for the beginning of the fifth season," added Lance Reddick (Broyles).

"We'll see what airs depending on what [Fox and WBTV] decide."

Joshua Jackson (Peter Bishop) also revealed that a "door" to a potential fifth run is "opened" in the upcoming episode 'Letters of Transit', airing April 20.

"If you watch that, you'll have an understanding of where [the writers] want to take the series," hinted Jackson. "The writers have given themselves a device by which we can tell a fifth season story without having to leave this season's story open."

Fringe continues tonight (April 13) at 9/8c on Fox. In the UK, the series airs on Sky1.